Bootstrapping Swarm and observatory data to generate candidates for the DGRF and IGRF-13

F Javier Pavón-Carrasco,Santiago Marsal,Fátima Martín-Hernández,Manuel Catalán,J Miquel Torta,J Manuel Tordesillas

doi:10.1186/s40623-020-01198-y

Abstract

As posted by the Working Group V of the International Association of Geomagnetism and Aeronomy (IAGA), the 13th generation of the International Geomagnetic Reference Field (IGRF) has been released at the end of 2019. Following IAGA recommendations, in this work we present a candidate model for the IGRF-13, for which we have used the available Swarm satellite and geomagnetic observatory ground data for the last year. In order to provide the IGRF-13 candidate, we have extrapolated the Gauss coefficients of the main field and its secular variation to January 1st, 2020. In addition, we have generated a Definitive Geomagnetic Reference Field model for 2015.0 using the same modelling approach, but focussed on a 1-year time window of data centred on 2015.0. To jointly model both satellite and ground data, we have followed the classical protocols and data filters applied in geomagnetic field modelling. Novelty arrives from the application of bootstrap analysis to solve issues related to the inhomogeneity of the spatial and temporal data distributions. This new approach allows the estimation of not only the Gauss coefficients, but also their uncertainties.

Highlights

The study of the Earth’s magnetic field is a hot topic in Earth Sciences, since it acts as a shield protecting our planet against the solar wind and other interplanetary interactions, of major importance in our technological era
Note that for the scalar F, we found slightly higher root mean square (RMS) errors following the magnetic equator for the three Swarm satellites, a pattern that was not found for the vector components and for the definitive geomagnetic reference field (DGRF) parent model
From the first parent model, extended from 1st July 2014 to 30th June 2015, we have derived our 2015 DGRF candidate of the core field truncated to spherical harmonic degree 13

Summary

Introduction

The study of the Earth’s magnetic field is a hot topic in Earth Sciences, since it acts as a shield protecting our planet against the solar wind and other interplanetary interactions, of major importance in our technological era. Since the early 1970s the International Association of Geomagnetism and Aeronomy (IAGA) has provided reference models of the geomagnetic main field every 5 years, the first model being published in 1971 (Zmuda 1971): the 1st generation of IGRF (IGRF-1, International Reference Geomagnetic Field). During 2018, the IAGA launched a new call for the submission of IGRF. Pavón‐Carrasco et al Earth, Planets and Space (2020) 72:152 candidates for the last generation. The IGRF-13 product includes the geomagnetic main field for 2020.0 and its temporal variation to extrapolate it from 2020.0 to 2025.0. It involves the revision of the previous IGRF-12 (Thébault et al 2015a), deriving the definitive geomagnetic reference field (DGRF) for 2015.0

Methods

Results

Conclusion